The present invention relates to turbine engines. In particular, the invention relates to internal cooling channel pedestals of an airfoil for a turbine engine.
A turbine engine employs a variety of airfoils to extract energy from a flow of combustion gases to perform useful work. Some airfoils, such as, for example, stator vanes and rotor blades, operate downstream of the combustion gases and must survive in a high-temperature environment. Often, airfoils exposed to high temperatures are hollow, having internal cooling channels that direct a flow of cooling air through the airfoil to remove heat and prolong the useful life of the airfoil. A source of cooling air is typically taken from a flow of compressed air produced upstream of the stator vanes and rotor blades. Some of the energy extracted from the flow of combustion gases must be used to provide the compressed air, thus reducing the energy available to do useful work and reducing an overall efficiency of the turbine engine.
Internal cooling channels are designed to provide efficient transfer of heat between the airfoils and the flow of cooling air within. As heat transfer efficiency improves, less cooling air is necessary to adequately cool the airfoils. Internal cooling channels typically include structures to improve heat transfer efficiency including, for example, pedestals (also known as pin fins). Pedestals link opposing sides of such airfoils (pressure side and suction side) to improve heat transfer by increasing both the area for heat transfer and the turbulence of the cooling air flow. The improved heat transfer efficiency results in improved overall turbine engine efficiency.
While the use of hollow airfoils provides for a flow of cooling air to extend the useful life of the airfoils, hollow blades are not as mechanically strong as solid blades. Improvements to the mechanical strength of hollow airfoils are needed to further extend their useful life.